An electrophotographic image forming apparatus such as a copying machine and a printer widely employs a photosensitive drum as an image bearing member. A general image forming operation using the photosensitive drum is carried out in the following manner. A charging section uniformly charges a surface of the photosensitive drum at a predetermined potential. An exposure section irradiates the surface of the photosensitive drum with LED light or the like, and the surface potential optically attenuates in part, to thereby form an electrostatic latent image corresponding to a desired image. A developing section develops the electrostatic latent image to form a toner image on the surface of the photosensitive drum. The toner image is transferred to a paper sheet when the paper sheet passes through a transferring region formed by the photosensitive drum and a transferring member, which are held in contact with or proximity to each other.
In order to achieve smooth image formation, it is necessary to appropriately grasp and notify a user of a remaining amount of toner as developer stored in the developing section that plays a major role in the image forming operation as described above. The user needs to replenish the toner to the image forming apparatus based on information on the remaining amount of the toner. In view of this, there is an image forming apparatus in which a toner container or a toner cartridge easily replaceable by the user is removably provided to a main body of the image forming apparatus.
The above-mentioned image forming apparatus includes a toner cartridge mountable to and removable from the main body of the image forming apparatus, a hopper serving as a toner buffer for temporarily storing toner supplied from the toner cartridge and replenishing the toner to the developing section, and detection means for detecting mounting and removal of the toner cartridge. With the hopper provided in the image forming apparatus, even when the removal of the toner cartridge is detected, the print job is continued and the user is prompted to mount the toner cartridge. In a case where a cover to be opened and closed when the toner cartridge is mounted and removed is opened, the image forming apparatus prompts the user to close the cover.
However, in the above-mentioned image forming apparatus, when the print job is continued in the case where the removal of the toner cartridge is detected, the remaining amount of toner replenished to the developing section from the toner cartridge is not taken into consideration.
That is, when it is detected that the toner cartridge is removed or the cover is opened under a state in which the toner is used up or almost used up, the toner cartridge is likely to be replaced with a new toner cartridge in a relatively early stage after the detection, which hardly disturbs continuation of the print job. On the other hand, when it is detected that the toner cartridge is removed or the cover is opened under a state in which the toner is sufficiently loaded, some trouble may occur in the image forming apparatus and the user may be unaware of the trouble. As a result, for example, the replenishment of the toner to the developing section is not smoothly performed so that the image quality is lowered, and an unnecessary replenishing operation is repeated even though the toner does not need to be replenished to the developing section so that the operation efficiency is lowered. Therefore, there is a risk that the continuation of the print job is seriously disturbed in the above-mentioned state.